In this instructable I will show you how to make a nice LED lamp made with an old jar and powered by a 10-12v power supply or a car cigarette plug. This can be easily made by a beginner, and I have laid everything out step by step.

Step 1: Tools and Parts Needed

You need:

10-12v wall plug / 12v car cigarette plug with a 5.5mm barrel plug.
Glass jar (I used an old marmalade jar)
9x5mm LEDs (any colour except red [red uses less power so I won't deal with them in this instructable], I used 6 yellow and 3 white LEDs)
A 5.5mm DC barrel jack
3x resistors (22 ohm for 10v, 33 ohm for 11v, 68 ohm for 12v)
1 wire, the length of the jar, stripped and tinned with solder.
Solder and a soldering iron.
A rasp (metal file, not pictured).

Step 2: Circuit Diagram of the Lamp

This lamp dissipates 0.3w, quite low power for the light it emits. This just uses LED strings and a resistor in parallel, so you can easily add more of these strings for more light.

Step 3: Soldering the Resistors

Take the resistors and solder one end of them together by twisting the ends together and flowing solder over them. Then solder them all to the positive pad of the DC jack.

Step 4: Solder the LEDs Together

Take the LEDs and solder three of them together in series, make sure that the negative side of the LEDs (the side with the larger electrode inside the bulb) to the positive side. An easy way to solder LEDs together is to tin all the LED leads with solder, then put the legs of the LEDs together and touch them with the soldering iron to reflow the solder and join them.

You can test the LED strings by touching the two ends to the connectors of a 9v battery. If it lights you have connected them all together correctly. Make three of these 3xLED strings for this project, although you could add as many of these strings as you like, as long as you don't exceed the amperage of the 10-12v power supply.

Step 5: Solder the LED Strings Together

Take the negative side of the LED strings and solder them together, then solder the stripped and tinned wire to where the strings meet. Ensure that the polarity is correct, otherwise some the the strings won't light.

Step 6: Solder the LEDs to the DC Jack

Using the same soldering technique used with the LEDs, solder the positive side of the LED strings to the three resistors. Then solder the wire to the negative pad of the DC jack. Plug it in to test it, if it doesn't work check if the polarity of the LEDs are correct.

Step 7: Drilling a Hole for the DC Jack in the Jar Lid

Drill a 5.5-6mm hole in the jar lid for the barrel jack. An easy way to do this is to punch a small hole in the lid with an awl or knife, then use successively larger drill bits to create a clean hole. Alternatively you could use a step drill and stop at the 6mm mark.

Step 8: Prepare the Surface of the Jar for Attaching the DC Jack

File down the sharp edge of the hole caused by the drill with a rasp, then use the rasp to scratch and rough the surface of the jar to bond the DC jack on. On the outside of the lid use an insulator like paint or tape to cover the front of the lid and inside of the hole you drilled.

Step 9: Bond the DC Jack to the Lid

Use a bit of epoxy resin or hot glue to bond the DC jack to the lid of the jar. You have to make sure the surface of the lid was thoroughly roughed and scratched, or else the resin/glue will have nothing to bond to, which will means the jack will easily come off when you plug it in.

I plugged in the DC plug to the jack to make sure it was lined up while the glue set, and if you are using 15 minute resin you can use some putty or blue-tack to hold the jack in place. Alternatively if you have a panel-mount DC jack you can drill some screw-holes into the lid and screw the jack in.

Step 10: Finishing Touches

Press the LED structure into shape, and remove any excess glue strands or epoxy spikes left over from the bonding. Then apply some pressure to the DC jack, if it comes off you need to rough up the surface of the lid more, and reapply the bonding material. Then screw on the lid and plug it in, and you should be done with this instructable!

If you have young children in the house you might want to seal the lid to the jar, especially if you're using a capacitive-dropper power supply, which can carry full mains power potential.